This proposal outlines a 5-year training program for Dr. Angelo Biviano, who is an assistant professor and academic cardiologist specializing in electrophysiology at Columbia University with a long term career goal to become an independent investigator. The proposed career development plan will incorporate the multidisciplinary resources available at Columbia to allow Dr. Biviano to acquire increased knowledge and expertise in clinical cardiac electrophysiology study design/methodology, including medical research dissemination, grantsmanship, and career development in academic electrophysiology. The co-sponsors, Dr. Hasan Garan (Professor of Medicine and Chief, Clinical Cardiac Electrophysiology) and Dr. Lori Mosca (Professor of Medicine and Director, Preventive Cardiology), will serve as mentors for this award, given their combined track records in mentoring in clinical cardiac electrophysiology (Dr. Garan) as well as clinical research design, implementation, dissemination, and grantsmanship (Dr. Mosca). In addition, an advisory committee of established clinical investigators (Dr. Marco Di Tullio and Dr. Mathew Maurer), biomedical engineers (Dr. Edward Ciaccio), and administrators (Dr. Jaime Rubin), will provide scientific and career advice. The proposed research plan consists of acquiring expertise in the use of signal processing and waveform analysis of ECGs and intracardiac electrograms to classify and localize arrhythmias that develop in patients after percutaneous catheter ablation for atrial fibrillation. The central hypothesis of the application is that new methods to classify and localize post-ablation atrial tachycardias using waveform and frequency analyses are required because current techniques employed during ECG and electrophysiology analyses are not sufficient (e.g., due to the confusing nature of atrial activation patterns that can occur after atrial fibrillation ablation, as well as the possibility of transforming/terminating the tachycardias during diagnostic pacing procedures). Dr. Biviano's previous work has shown that atrial tachycardias occurring after atrial fibrillation ablation can have atypical morphologies and that novel methods can be used to improve the calculation of atrial activation rates.1-3 Specific aims of the research plan are to use ECG waveform and cardiac frequency analyses in patients manifesting atrial tachycardias after percutaneous catheter ablation for atrial fibrillation to: 1) diagnose left atrial versus right atrial tachycardias; 2) diagnose left atrial focal versus macroreentrant tachycardias, as well as different types of macroreentrant tachycardias; 3) distinguish atrial tachycardias from coarse atrial fibrillation. Preliminary data demonstrates that the research plan is feasible. The proposal is innovative because it will focus on improving upon the limitations of currently employed diagnostic atrial mapping and pacing techniques by utilizing novel concepts and methodologies not previously applied to patients after atrial fibrillation ablation. The proposal is relevant because it will lead to more successful and efficient ways to diagnose atrial arrhythmias in patients after atrial fibrillation ablation.